The invention relates to an apparatus for the burn-in of electronic components such as semi-conductors and the like.
Integrated circuits (ICs), after manufacture and prior to use in a computer system, undergo a variety of tests to ensure they are defect free and will perform as intended. One of the tests conducted is known as burn-in.
Test systems for component testing are well known; for example, semi-conductor life tests in burn-in chambers are common. The process of burning-in typically consists of applying a load to the components being tested at elevated temperatures. This allows identification of weak or faulty components and thus procludes their ultimate use, such as in a computer system.
In addition to burn-in ovens or hot air ovens, other technologies used for this purpose are open loop conduction heating, such as hot plates and thermal probes and liquid bath systems.
The burn-in ovens are by far the most prevalent test device and method used. Second in importance are the liquid burn-in bath methods.
In order to apply a load to the components under test, driver electronics are used which must be isolated from the hot thermal environment of the high temperature oven or liquid bath. This means that the driver electronics must be some distance from the devices under test (DUTs) which compromises frequency limits. Further, DUT trays must be high temperature material which adds to the costs of the testing procedure. The burn-in ovens, or forced air systems, typically have plus or minus 3.degree. C. gradients throughout the chamber as required by MIL-STD-883. However, device heat dissipation makes determining the actual case temperatures (and therefore, junction temperatures) very difficult. Materials used in the chamber must be rated at the highest operating temperature, i.e. sockets, capacitors, resistors, connectors and PC board material. Semi-conductors cannot be used on the PC board above 75.degree. C. because of their unreliability at these temperatures. High frequency applications (approximately 5 mHz) requires multi-layer polyimide, PCBs, mother boards, daughter boards and extender boards to be used. High pin count devices require very high I/Os through chamber walls or a compromise must be made. Further, clock cards outside the chamber driving long distances (typically as long as 30 inches) compromise the high frequency operation. In liquid bath systems, the problems are the same as the burn-in ovens. Further, they are more expensive to operate, more inconvenient to operate and clock circuits cannot be put into the bath.
Briefly, some of the common problems with current technology is that the driver electronics are remote from the DUTs. This affects signal quality, the maximum signal frequency that can be used and results in signal skew, cross talk and overshoot. The I/O through the oven walls is not especially suitable for high pin count VLSI components and there is a practical limit to the number of I/Os and the possibility of impairment of signal quality. The trays used in the ovens are expensive, high temperature material. There are temperature variations throughout the oven due to flow dynamics and one is never really sure of the actual DUT junction temperature. Perhaps the most severe problem is the large monolithic ovens are not amenable to small lot burn-in, independent temperature cycling or independent DUT cool down under bias.
It would be desirable to have the driver electronics as close as possible to the DUT preferably located on the burn-in tray and to conduct the burn-in in ambient conditions. Most importantly, accurate independent temperature control of each DUT on a burn-in tray would be desirable.